Distributed communication services in the Masix system

Abstract

Masix is a distributed multi-server operating system based on the Mach microkernel, with multiple personality support. Its main feature is a distributed generic layer (DGL), which offers distributed services to the personalities. The distributed multi-server architecture of Masix grants it a high modularity, but also raises many issues, such as transparency, security and performance, which cannot be solved without adequate communication services. To provide total transparency, we extend the traditional Mach communication model to a workstation network by interposing a generic network server (GNS) between the tasks and the microkernel. We defined a global name service, based on a name resolution protocol, which allows any pair of Mach remote tasks to communicate transparently, using the local Mach IPC semantics. Our name server also provides local and remote authentication mechanisms, based on digital signatures and a secret key algorithm. To prevent eavesdropping, all remote communications are transparently encrypted by the GNS, using a public key algorithm. These security measures can be easily merged into the name service, to yield a secure distributed name resolution protocol. Microkernel based-systems are traditionally criticized for their relatively poor performance. As far as network services are concerned, experiments show that a good performance level can be reached, provided that the distinctive features of microkernels are taken into account.